Shaping method and apparatus of thin metal sheet

ABSTRACT

The invention provides a method and an apparatus capable of accurately shaping, within a short time, cubic products such as trial products for press molding for mass production without limitation of a molding shape. While edge portions of a blank are clamped, a mold punch having a molding shape is pushed from a sheet thickness direction to conduct rough forming. While the mold punch is kept pushed, shaping is conducted by use of a rod-like tool from an opposite side to the mold punch sandwiching the sheet thickness.

TECHNICAL FIELD

[0001] This invention relates to a shaping method of a thin metal sheet and an apparatus for the method.

BACKGROUND ART

[0002] Methods and means for processing a thin metal sheet into a cubic shape are described in JP-A-7-132329, for example. In this prior art technology, edge portions of a thin metal sheet are fixed to a frame-like table capable of moving up and down, and a pole-like push body is implanted inside a space encompassed by the frame-like table. To conduct shaping, the pole-like push body is brought into contact with a lower surface of the thin metal sheet, and a rod-like tool capable of moving in a Z-axis direction is positioned on the upper surface side of the thin metal sheet. While the rod-like tool is moved round the push body, the frame-like table is lowered so as to serially cause plastic deformation of the thin metal sheet.

[0003] This shaping method is believed suitable for producing a trial product. Since the rod-like tool is allowed to describe a contour line orbit to serially shape the shape of the overall product, however, the method is time-consuming from the start till the end of shaping, and mass-production of 500 pieces/month is difficult to attain in practice.

[0004] Though this shaping method can shape a simple expanding shape such as a cone and a pyramid, the method is not free from the limitation that it cannot easily shape an angular portion of a longitudinal wall and cannot either shape easily a product having grooves and protrusions on its bottom surface having a large area.

[0005] Since the prior art technology is based on expansion molding exclusively utilizing “stretching” of a material as its processing principle, the resulting product is inferior in a large drop of its sheet thickness and its dimensional accuracy to those obtained by press molding. Therefore, the method is not entirely suitable for trial production for mass-producing press moldings and for producing trial products.

DISCLOSURE OF THE INVENTION

[0006] To solve the problems described above, it is a first object of the invention to provide a shaping method that can shape accurately and moreover, within a short time, cubic products such as trial products for mass-producing press moldings from a thin metal sheet without limitation of a molding shape.

[0007] It is a second object of the invention to provide an apparatus that can shape accurately and moreover, within a short time, cubic products such as trial products for mass-producing press moldings without limitation of a molding shape, and has a simple construction.

[0008] A shaping method of a thin metal sheet for accomplishing the first object described above comprises the steps of clamping edge portions of a thin metal sheet; pushing under this state a mold punch finished to a product shape from below a sheet thickness direction; conducting a forming operation to shape a rough forming body having a top portion and side portions; and finishing the rough forming body to a product shape by use of a tool capable of moving three-dimensionally with the mold punch as a mold surface from an opposite side to the mold punch sandwiching the sheet thickness while the mold punch is kept under a pushed state.

[0009] The step of finishing the rough forming body to the product shape may employ a method that uses a rod-like tool and cause the rough forming body to undergo local plastic deformation. Furthermore, it is possible to use an elastic tool in a first stage and to push the tool to the mold punch from an opposite side to the mold punch sandwiching the sheet thickness so as to cause local compression molding, and to conduct finish shaping by use of the rod-like tool in the second stage. According to the latter, a high precision molding operation can be conducted even in a complicated shape locally having projections and recesses.

[0010] To accomplish the second object, the invention provides a molding apparatus of a thin metal sheet comprising a bed equipped with a mounting frame;

[0011] a plurality of wrinkle support devices arranged on the bed with intervals each other for clamping edge portions of a thin metal sheet in the sheet thickness direction; a mold punch arranged inside a recess chamber which is formed in the bed more inward than the wrinkle support devices;

[0012] a mold punch elevation device for pushing the mold punch into the thin metal sheet supported by the wrinkle support devices; a secondary molding device fitted to the mounting frame movably in three-axis directions; and a tool fitted to the secondary molding device for conducting shaping of a rough forming body shaped by the mold punch in cooperation with the mold punch.

[0013] According to this construction, a mold punch corresponding to a product shape is prepared and is fitted to the mold punch elevation device and high precision shaping can be carried out.

[0014] The wrinkle support devices are arranged on the bed and do not move up and down. In other words, unlike the prior art shaping apparatus, a frame-like table for clamping the edge portions of the thin metal sheet in the direction of the sheet thickness, capable of moving up and down, is not necessary. The invention neither requires a mechanism for lowering the frame-like table in accordance with the progress of shaping nor balance movement control. Therefore, the construction of the apparatus can be simplified. In addition, the height of the apparatus can be lowered, and conveying of the thin metal sheet and withdrawal of the product can be carried out at a position close to a ground level.

[0015] The invention is suitable for shaping large-scale products such as outer panels typified by automobile components such as a fender and a food outer panel, airplane components, building materials, kitchen products, bath products and electric appliances.

[0016] Other features and advantages of the invention will become more apparent from the following detailed description, but the invention is not particularly limited to the construction of the embodiments so long as the basic feature of the invention is satisfied. It will be therefore obvious that those skilled in the art can make various changes and modifications without departing from the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a longitudinal sectional side view showing a state before the start of shaping in a metal thin sheet shaping apparatus according to an embodiment of the invention.

[0018]FIG. 2 is a longitudinal sectional side view showing a state of use of the apparatus according to the invention.

[0019]FIG. 3 is a plan view.

[0020]FIG. 4 is a longitudinal sectional front view.

[0021]FIG. 5 is a partial cut-away side view showing the arrangement of a tool for finishing a product into shape and a secondary molding device.

[0022]FIG. 6 is a partial enlarged side view showing a state where shaping is carried out by use of a first kind of a tool for finishing the product into shape.

[0023]FIG. 7 is a partial enlarged side view showing a state where shaping is carried out by use of a second kind of a tool for finishing the product into shape.

[0024]FIG. 8 is a partial perspective view showing another example of the secondary molding device according to the invention.

[0025]FIG. 9 is a partial sectional view of FIG. 8.

[0026]FIGS. 10A, 10B and 10C are explanatory views each showing an example of a shaping tool.

[0027]FIGS. 11A and 11B are explanatory views each showing an example of a final shaping tool.

[0028]FIGS. 12A to 12D are sectional views each showing step-wise a shaping example according to the invention.

[0029]FIGS. 13A to 13C are partial sectional views each showing step-wise another example of the shaping example according to the invention.

[0030]FIGS. 14A to 14C are partial sectional views each showing step-wise still another shaping example according to the invention.

[0031]FIG. 15 is a perspective view showing an example of a product to which the invention is applied.

[0032]FIG. 16 is a perspective view showing another example of a product to which the invention is applied.

[0033]FIGS. 17A to 17C are sectional views each showing step-wise a shaping step of the product shown in FIG. 16.

DETAILED DESCRIPTION OF THE INVENTION

[0034] Embodiments of the invention will be hereinafter explained with reference to the accompanying drawings.

[0035] FIGS. 1 to 4 show a shaping apparatus of a thin metal sheet according to a first embodiment of the invention.

[0036] Reference numeral 1 denotes a bed or frame (hereinafter called “bed”). A recess chamber 11 opening to an upper surface 10 is defined in a center region. An elevation actuator 2 such as a hydraulic cylinder is fixedly disposed at a lower part of the recess chamber 11. A mold-fitting disk 3 is interconnected to an output portion of the elevation actuator 2. A mold punch 4 finished into a cubic shape corresponding to a shape of a product is removably fitted to the mold-fitting disk 3.

[0037] The mold punch 4 generically represents those that are called “formed type” or a “master mold”, and includes a top portion and side portions. The mold punch 4 is generally formed of a metal material such as a steel material, but may be formed of FRP in some cases. The mold punch 4 locally has a concavo-convexity portion 40 besides a flat surface shape, and the concavo-convex portion 40 includes a protrusion, a projection, a recess, a groove, and so forth.

[0038] Reference numeral 5 denotes a plurality of wrinkle support devices arranged with a predetermined interval each other so as to encompass the opening of the recess chamber 11 on the bed outside the recess chamber 11. Each wrinkle support device 5 includes a die 50 for supporting an edge portion of a thin sheet W, a support disk 51 opposing the die 50, a block-like main body 5 a having a support actuator 52 for pressurizing the support disk 51 and a movement actuator 5 b fixed on the bed at the back of the main body 5 a and having an output portion interconnected to the main body 5 a, as shown in FIG. 6. The wrinkle support devices 5 can be operated separately. The number of the wrinkle support devices 5 and their operation forms (the support actuator 52 alone or the support actuator 52 and the movement actuator 5 b) are selected in accordance with the shape of the thin sheet, its mechanical properties and shapes to be molded.

[0039] Reference numeral 6 denotes a secondary molding device capable of moving above the bed 1. The secondary molding device 6 includes a mounting frame 6 a provided to the bed 1 so as to avoid the wrinkle support devices 5 and a main shaft body 6 b mounted to the mounting frame 6 a. The main shaft body 6 b includes a tool holder 6 c to which a tool 7 for local compression molding and a tool 8 for shaping are removably fitted as will be explained later.

[0040] The mounting frame 6 a includes four or more columns 69 whose lower portions are fixed to the bed 1, a pair of parallel X-axis rails 60 transversely supported by the top portions of these columns 69, and a Y-axis rail 61 supported by the X-axis rails 60 and 60. A numerical control type driving mechanism 62 for moving the Y-axis rail 61 along the X-axis rails 60, 60 is mounted to the Y-axis rail 61.

[0041] The main shaft body 6 b is mounted on the Y-axis rails 61, and has a numerical control type driving mechanism 63 for moving along the Y-axis rail 61. The main shaft body 6 b has at its lower part the tool holder 6 c extending toward the bed. A numerical control type driving mechanism 64 for moving the tool holder 6 c or a slide having the tool holder 6 c thereon in a Z-axis direction is mounted to the top portion of the main shaft body 6 b. The driving mechanisms 62, 63 and 64 are electrically connected to a controller, not shown, and can freely adjust the position of the tool removably fitted to the tool holder 6 c in accordance with the control signal from the controller.

[0042] The tool holder 6 c has a chuck mechanism. The chuck mechanism is arbitrary. This embodiment includes an extensible chuck 600 having a fastening nut 601 and a split sleeve 602 fitted into a taper hole of the chuck 600 as shown in FIG. 5.

[0043] Reference numeral 7 denotes the tool for local compression-molding. This tool 7 includes a fitting portion 70 to the split sleeve 602 of the tool holder 6 c and an elastomer 71 such as urethane rubber for locally applying a strong pressure to the thin metal sheet W and shaping it in cooperation with the concavo-convexity portion 40 of the mold punch 4 as shown in FIGS. 4 and 5.

[0044] Reference numeral 8 denotes a tool for shaping, formed of a hard material such as a super-hard alloy. This tool 8 includes a fitting portion 80 to the split sleeve 602 of the tool holder 6 c and a push portion 81 for shaping detailed shapes of the thin metal sheet W and finishing the work as a whole in cooperation with the mold punch 4 as shown in FIG. 5. The fitting portions 70 and 80 of both the tools 7 and 8 have the same outer diameter.

[0045] The construction shown in the drawings represents a mere example of the invention, and other constructions may well be employed, too.

[0046] For example, though this embodiment uses an AC servo motor as the moving mechanism of the secondary molding device 6, a linear motor may be used instead, as shown in FIGS. 8 and 9. Reference numeral 65 denotes a guide rail. Reference numeral 66 denotes a magnetic plate. Reference numeral 67 denotes a coil slider. Reference numeral 68 denotes a linear scale.

[0047] The tool 8 for shaping may have a spherical push portion 81 at its distal end as shown in FIG. 10A. Alternatively, as shown in FIG. 10B, it may have at the distal end a recess portion 82 having curvature and rotatably dispose a hard ball 81′ in the recess portion 82. Still alternatively, a liquid charging port 83 communicating with the recess portion 82 may be formed as shown in FIG. 10C to supply a lubricant thereinto.

[0048] The tool 8 for shaping may be rotatable relative to the tool holder 6 c. FIG. 11A shows this example. A rotary shaft 6 d is disposed at the lower part of the tool holder 6 c so as to be relatively rotatable, and the tool 8 is fitted to the rotary shaft 6 d eccentrically with the axis of the rotary shaft 6 d. Any rotation means can be used, however, in this example, a driving motor 6 e is mounted to the tool holder 6 c and the motor output is transmitted to the rotary shaft 6 d through a transmission element 6 f such as a pulley and a gear.

[0049] Next, a shaping method of a thin metal sheet according to the invention will be explained.

[0050] To start shaping, the mold punch 4 finished to the molding shape is fixed to the mold-fitting disk 3 by use of a bolt and a nut. When the preparation is ready in this way, the thin metal sheet W is conveyed onto the bed 1 by conveyor means such as a magnet chuck. In that case, it is preferable that the movement actuator 5 b of the wrinkle support device 5 has been operated to move back the main body 5 a and to move the support disk 51 towards the open side by each support actuator 52 of the wrinkle support device 5. Then, the main body 5 a is moved forward with conveying of the thin metal sheet W and the edge portions of the thin metal sheet W are inserted between the main body 5 a and the die 50. The necessary support actuator 52 is operated to lower the support disk 51 to clamp the edge portions of the thin metal sheet W with the die 50.

[0051]FIGS. 1 and 12A show this state. The thin metal sheet W is spread over the recess chamber 11 and the mold punch 4 is positioned below the thin metal sheet W. The secondary molding device 6 is located at the side standby position. The tool 7 for local compression molding or the tool 8 for shaping is fitted at this time to the tool holder 6 c in accordance with the product shape. When the product has a relatively simple shape such as a shape not having concavo-convexity at its top, the tool 8 for shaping may be used. Otherwise, the tool 7 for local compression molding is fitted for the first stage shaping.

[0052] Next, the elevation actuator 2 is operated to raise the mold punch 4. The mold punch 4 forcibly comes into contact with the lower surface of the thin metal sheet W. As the mold punch 4 successively rises, the thin metal sheet W is caused to undergo plastic deformation in the direction of the sheet thickness along the shape of the mold punch 4, and is roughly formed into a cubic shape having the top and sidewall portions by the squeeze operation. Symbol W1 denotes a rough forming body.

[0053] The pressing force of the support actuator 52 of the necessary wrinkle support device 5 is reduced during rough forming in accordance with the characteristics such as the shape, sheet thickness, and elongation of the thin metal sheet W, the material, to promote the flow of the material. When this means is not yet sufficient, the movement actuator 5 b is operated to move forth the main body 5 a. In consequence, the material can be prevented from tearing, and the overall shape is shaped with the exception of the mold punch local portion (protuberance in this embodiment) 40 as shown in FIG. 12B.

[0054] Next, while the mold punch 4 is kept at the raised position, the tool 7 for local compression molding is moved immediately above the mold punch local portion 40. This positioning can be achieved by the movement of the Y-axis rail 61 relative to the X-axis rails 60 by the driving mechanism 62 and the movement of the main shaft body 6 b relative to the Y-axis rail 61 by the driving mechanism 63.

[0055] Next, the tool 7 for local compression molding immediately above the mold punch local portion 40 is moved by means of the driving device 64 in the Z-axis direction. Consequently, the blank portion WP that has been out of contact from, gently contact with, the mold punch local portion 40 undergoes compression molding as the elastomer 71 is pushed against the mold punch local portion 40, to profile the mold punch local portion 40 as shown in FIG. 12C. Symbol WP1 denotes a compression molding portion.

[0056] Next, the main shaft body 6 b is moved sideward, the chuck is loosened and the tool 7 for local compression molding is removed from the tool holder 6 c and is replaced by the tool 8 for shaping.

[0057] The main shaft body 6 b is moved in the X-, Y- and Z-axis directions by the respective driving mechanisms 62, 63 and 64, and the push portion 81 (81′) of the tool 8 for final shaping is brought into high pressure contact with the compression molding portion WP1 in the region of the mold punch local portion 40 to cause local plastic deformation. In this way, the precise shape of the details can be shaped as shown in FIG. 12D. Symbol WP2 denotes a finish local portion. When the main shaft body 6 b is moved in the X-, Y- and Z-axis directions by the respective driving mechanisms 62, 63 and 64, the portions other than the mold punch local portion 40, such as the sidewalls and the boundary portion between the sidewall and the ceiling can be finished to the final profile.

[0058] In the first step of the invention, the thin metal sheet W is subjected to free forming inclusive of the squeeze component by use of the mold punch 4. Therefore, it is not necessary to move the tool 8 for shaping in the contour line orbit in the second step. In other words, shaping may well be carried out while the thin metal sheet W is moved three-dimensionally in accordance with the product shape and while it is continuously pushed to the mold punch 4.

[0059] After shaping is completed as described above, the main shaft body 6 b is moved to the side standby position by the driving mechanisms 62, 63 and 64 and the mold punch 4 is moved to the lower limit. Consequently, the mold punch 4 is removed from the product W2 and the product W2 remains while being held by the wrinkle support devices 5. Clamping by the wrinkle support devices 5 is released and the product W2 is thereafter taken out.

[0060]FIGS. 13A to 13C show another example of local compression molding and final shaping. The mold punch 4 has a recessed local portion (recess or groove) 40 and moreover, a protuberance 400 at the bottom of the local portion.

[0061] In this case, the tool 7 for local compression molding is moved at least in the Z-axis direction, or serially in the X-axis direction and/or in the Y-axis direction and then in the Z-axis direction, while rough forming is conducted by use of the mold punch 4 as shown in FIG. 13A. When this operation is conducted at least once, the non-molded portion WP is pushed into, and brought into high-pressure contact with, the recessed local portion 40 as the elastomer 71 strongly pushes as shown in FIG. 13B. At this time, the compression molding portion WP1 has not yet been brought sufficiently into contact with the recessed local portion 40 by the strong pressure of the elastomer 71. Therefore, the tool 8 for final shaping is serially moved under numerical control to bring the compression molding portion WP1 into contact with the bottom protrusion 400 forcibly as shown in FIG. 13C. Consequently, high precision shaping can be carried out.

[0062]FIGS. 14A and 14B show the case where the mold punch 4 has a convex local portion (projection or protrusion) 40 and moreover, a recess portion 401 at the top of the local portion. In this case, too, the non-molded portion WP of the rough forming body W1 is subjected to local compression molding by use of the tool 7 for local compression molding as shown in FIG. 14A, and contact movement of the tool 8 for shaping is used for shaping detailed portions and for finishing. In this way, high precision shaping can be carried out.

[0063] When a hard ball 81′ capable of freely rotating is used as the tool 8 for final shaping as shown in FIG. 10B, contact with the material changes from sliding contact to rolling contact. Therefore, it becomes possible to prevent exothermy due to friction, to reduce the occurrence of machining scratches of the shaped article and to prevent spring-back.

[0064] When the tool 8 for final shaping is rotatable as shown in FIG. 11A, shaping accuracy can be improved because as shown in FIG. 11B pressure is applied to the shaping region eccentrically as well.

[0065] The method of the invention can take various forms of use.

[0066] 1) The method of the invention includes the step of operating only a part of the plurality of wrinkle support devices 5 to conduct local fixing and local clamping. In other words, the method includes the step of keeping the pressing force of the support actuators 52 of the necessary wrinkle support devices 5 unloosened or releasing the pressing force of the support actuator 52 of the necessary wrinkle support devices 5 to the free state.

[0067] 2) When the shape to be shaped is smooth such as a hood, it is possible to omit the local compression molding step and to conduct shape-fixing for eliminating spring-back by contact movement by the tool 8 for shaping in succession to rough forming, or to conduct shaping of the fine portions and finish shaping.

[0068] The invention is suitable for trial production of various large-scale cubic products. For example, the invention can easily and accurately produce outer panels of an automobile typified by a fender and a hood outer plate shown in FIG. 15 and a hood inner plate shown in FIG. 16.

[0069] Explanation will be given in further detail. The product shown in FIG. 16 has a size of 885×970 mm and includes sidewalls WS and a ceiling wall WT connected at right angles to the sidewalls WS. Moreover, the ceiling wall WT has a complicated shape having a plurality of groove-like recess portions WP2. The groove-like recess portion WP2 has a bottom width of 20 mm, an open width of 32 mm and a depth of 13 mm.

[0070] To shape such a product, the invention uses the mold punch 4 having groove-like local portions 40 corresponding to the groove-like recess portions WP2 as shown in FIG. 17A and pushes the punch 40 into the thin metal sheet to freely shape the rough forming body W1. Next, the non-molded portion WP of the rough forming body W1 is subjected to local compression molding by bringing the tool 7 for local compression molding into high-pressure contact with the local portion 40 as shown in FIG. 17B. The tool 8 for shaping is then used to replace the tool 7 for local compression molding. The tool 8 is moved while keeping contact with the local portion 40 to conduct finish shaping as shown in FIG. 17C. In the rough forming stage, the sidewalls WS do not keep close contact with the side surface 41 of the mold punch, but keep floating. When the tool 8 is moved three-dimensionally and the sidewalls WS are pushed to the mold punch side surface 41, however, sharp sidewalls can be shaped.

[0071] The shaping condition used in practice is as follows.

[0072] The thin metal sheet is an SPCD plated steel sheet having a sheet thickness of 0.7 mm and a size of 1,050×1,130 mm.

[0073] The rough forming condition includes a wrinkle support force of 70 tonf and uses an oil lubricant as a lubricant.

[0074] As the elastic tool urethane rubber having a diameter 50 mm×70 mm is used and local compression is conducted under a push condition of 20% compression.

[0075] As the rod-like tool, a super-hard alloy having a diameter of 10 mm is used, and finish shaping is conducted under the moving condition (shaping pitch in the direction of height) of 0.5 mm.

[0076] As a result, the shaping time is 2 hours, and accuracy of the product obtained is ±0.5 mm, which satisfy the required quality. The sheet thickness reduction ratio is within 20%.

[0077] Industrial Applicability

[0078] The invention is suitable for trial production of various large-scale cubic products. 

1. A shaping method of a thin metal sheet comprising the steps of: clamping edge portions of a thin metal sheet; pushing under this state a mold punch finished to a product shape from below a sheet thickness direction; conducting forming to shape a rough forming body having a top portion and side portions; and finishing said rough forming body to a product shape by use of a tool capable of moving three-dimensionally with said mold punch as a mold surface from an opposite side to said mold punch sandwiching the sheet thickness while said mold punch is kept under a pushed state.
 2. A shaping method of a thin metal sheet according to claim 1, wherein said step of finishing to the product shape is carried out by using a rod-like tool and causing said rough forming body to undergo local plastic deformation.
 3. A shaping method of a thin metal sheet according to claim 1, wherein said step of finishing to the product shape is carried out in two stages of using an elastic tool and pushing said elastic tool to said mold punch from an opposite side to said mold punch while sandwiching the sheet thickness to cause local compression molding, and shaping said rough forming body to a finish shape by use of a rod-like tool.
 4. A molding apparatus of a thin metal sheet comprising: a bed equipped with a mounting frame; a plurality of wrinkle support devices arranged on said bed with intervals among them and clamping edge portions of a thin metal sheet in a sheet thickness direction; a mold punch arranged inside a recess chamber which is formed in said bed more inward than said wrinkle support devices; a mold punch elevation device for pushing said mold punch into said thin metal sheet supported by said wrinkle support devices; a secondary molding device fitted to said mounting frame movably in three-axis directions; and a tool fitted to said secondary molding device for conducting shaping of a rough forming body shaped by said mold punch in cooperation with said mold punch.
 5. A molding apparatus of a thin metal sheet according to claim 4, wherein said tool is two kinds of tools, that is, a local compression molding tool having a fitting portion and an elastomer, and a rod-like hard tool, the tools being removably fitted to a tool holder of said secondary molding device. 